This invention relates to security locks. More particularly although not exclusively it discloses a lock release apparatus for providing delayed passage through a doorway or the like.
With exit doors it is often necessary to provide a delayed egress system. While still allowing an exit such systems impose a predetermined delay between operation of the latch or push bar and the release of the door. With appropriate monitoring and alarms security staff are thereby allowed time to react before a person leaves the premises. Existing systems use a microwave or passive infrared beam motion detector which is directed downwardly in front of the door. Others use passive beams with micro switches and hard wiring through the doors or frames to communicate with the lock. Movement of persons attempting to use the door is detected and a timer is activated for release of the lock after a predetermined delay of say 15 seconds. The disadvantage of existing movement detecting systems is that the timer can be xe2x80x9cfooledxe2x80x9d into releasing the lock by passing a card, mirror or the like under the door from outside to intercept the beam. Extraneous light can also trigger the motion detectors to release the lock.
It is therefore an object of this invention to ameliorate the aforementioned disadvantages and accordingly a lock release apparatus for a movable barrier such as an exit door is disclosed, said apparatus including a pulled tuned active infrared a beam tramsmitter and receiver, timer means for releasing said lock after a predetermined delay, trigger means operatively connecting said timer means and said receiver for initiating operation of said timer means and reflector means associated with a latch handle, push bar or the like on said door, in use of the apparatus said transmitter being disposed to direct a beam onto said reflector at an orientation such that the reflection thereof is detected by said receiver and whereby movement of said handle, push bar or the like for exit terminates said reflection or shifts said reflection away from said receiver to thereby trigger said timing means to release the lock after a predetermined delay.
Preferably said beam is of a pulsed infrared light. The frequency of the pulses corresponds to the received tuned frequency. This insures that the received is only reacting to the transmitted signal. It also improved the power to range ratio.
It is further preferred that alarm means be activated during said predetermined delay.